To Heart is a landmark in Japanese adult PC gaming. Released in 1997, the game is a visual novel and showed how adult themes could be woven into a moving story. It influenced a generation of visual novels.
It spawned a sequel in 2004, ToHeart2, anime, manga and, now, a straight up rip off. Adult game developer Milk Pai is releasing 18-and-up game Dere Suku this August. In the above image, the art is on the left is ToHeart2 character Tamaki. On the right is Dere Suku character Maki.
In the below image, ToHeart2 character Sasara Kusugawa — she appeared only in the PC version of the game and not the PS2 version. The character on the right is Tomo from Milk Pai's upcoming erotic game.
とある新作のエロゲが『ToHeart 2』をパクリまくりな件 [オレ的ゲーム速報＠刃]